1. Field of the Invention
The present invention relates to monoclonal antibodies recognizing membrane phospholipase A.sub.2 ; hybridomas producing said monoclonal antibodies; a method for producing said monoclonal antibodies; and immunoassays using said monoclonal antibodies.
2. Description of the Prior Art
Phospholipase A.sub.2 (PLA.sub.2) (EC 3.1.1.4) is an enzyme which can hydrolyze the fatty acyl ester bond at the sn-2 position of glycerophospholipids. It is well known that the enzyme is present in the pancreas or snake venom, and it has been observed that the level of pancreatic PLA.sub.2 in blood becomes increased when suffering from pancreatitis (Ogawa et al., Gendai Iryou, 20 (1988) 3013-3017). The PLA.sub.2, however, is not only present in the external secretion system, but also found in almost all of the cells in a living body, although the amount thereof is very small (Van den Bosch, H. in Phospholipids (Hawthrone, J. N. and Ansell, G. B. eds.) (1982) pp. 313-357, Elsevier/North-Holland Biomedical Press, Amsterdam). It is believed that the enzyme would play an important role in the metabolic regulation of membrane phospholipids and in the eicosanoide biosynthesis through arachidonic acid (Van den Bosch, H., Biochim. Biophys. Acta (1980) 604, 191-246), and would relate to inflammation and cellular injury through the direct action or through its metabolites such as lysophospholipids, leukotrienes, platelet-activating factor and lipid peroxides (Vades, P. et al., Lab Invest. (1986) 55, 691-404).
It was revealed that membrane PLA.sub.2 (PLA.sub.2 M) isolated from human splenic membrane fraction was the different type of PLA.sub.2 from pancreatic PLA.sub.2 by analysis of its protein primary structure (Kanda, A. et al., Biochem. Biophys. Res. Commun. (1989) 163, 42-48), and it was also found that PLA.sub.2 M was induced by an inflammatory mediator such as IL-1 and TNF and secreted out of the cells (Nakano, T. et al., FEBS Lett. (1990) 261, 171-174). Moreover, a comparison between PLA.sub.2 M and PLA.sub.2 purified from rheumatoid arthritic synovial fluid showed that they are identical in their structure and reactivity (Kramer, R. M. et al., J. Biol. Chem. (1989) 264, 5768-5775).
From a clinical point of view, an increase of the PLA.sub.2 enzymatic activity was found in the blood of patients with an infectious disease such as septicemia, pustular psoriasis, Crohn's disease, and rheumatoid arthritis. Further, it was found that the PLA.sub.2 enzymatic activity is induced by intracutaneous injection of bacteria, viruses, or other inflammatory inducers into an animal (Vades, P. et. al., supra).
To date, however, no report has appeared concerning the assay of PLA.sub.2 M, and it has not yet been shown whether an increase of the PLA.sub.2 enzymatic activity accompanying the aforesaid diseases is caused by PLA.sub.2 M or not.
As described above, because the PLA.sub.2 enzymatic activity in blood is increased when suffering from rheumatism, septicemia, pustular psoriasis, Crohn's disease, or the like, it has been expected that the diagnosis of these diseases can be realized from the measurement of PLA.sub.2 M and an assay of PLA.sub.2 M has been desired.